The concept of pressureless irrigation has been first proposed by an authorized patent “a novel pressureless irrigation device” with a publication number of CN102160518A. Pressureless irrigation is an irrigation method in which an elevation of an irrigation water source is equal to that of an irrigator, which is derived from a definition of “negative pressure irrigation”. The patent CN102160518A is invented to provide a novel pressureless irrigation device which is as efficient as the negative pressure irrigation, more convenient to use, more durable and highly reliable. A patent literature with the publication number of CN102160518A discloses a novel pressureless irrigation device which includes a water supply tank, a water level control pool, a water conveying main pipe, a confluence pipe and a plurality of irrigators (referring to a patent specification of CN102160518A).
The patent of a novel pressureless irrigation device with the publication number of CN102160518A adopts the irrigator (referring to the patent specification of CN 102160518 A) using a U-shaped concrete trough as a basic structure, and has the following defects. Firstly, high-precision concrete pouring molding equipment is required in on-site construction; a series of technical problems exist such as expansion joint anti-seepage treatment and the like; input is large and construction is difficult. Secondly, the U-shaped concrete trough made of brittle material is easy to be damaged by frost-heaving, uneven subsidence, tillage machine operation and the like; most importantly, the height of a soil saturated water layer cannot be adjusted for supplying water to a crop root system layer by rising of soil capillary water. When water consumption for crop transpiration is not high, and when the soil water continues to rise to a soil surface to form soil evaporation between plants and to cause accumulation of salt in the surface soil, the problem cannot be solved by reducing the height of the soil saturated water layer. Similarly, a common problem of irregular seedling emergence caused by inadequate water supply of the surface soil at a seedling stage after underground irrigation sowing also cannot be solved by a method of raising the height of the soil saturated water layer. The patent of a novel pressureless irrigation device with the publication number of CN102160518A adopts a water supply tank type water level adjustment and water supply device which has the following defects. Firstly, a special control water level adjustment mechanism and control water level gauge are not provided so that the control water level is very difficult to be adjusted accurately, and requirement of accurately and conveniently adjusting the control water level at any time of a novel irrigator of the novel pressureless irrigation device of the present cannot be satisfied. Secondly, a water supply tank of the water supply tank type water level adjustment and water supply device needs to operate in a closed state (referring to the patent specification of CN 102160518 A), which cannot be filled with water at any time, and is inconvenient to adopt a photovoltaic water pumping mode.